riptide_autonomy

This package contains OSU UWRT's competition task code. UWRT uses a behaviortree-based autonomy system, featuring the BehaviorTree.CPP library, and uses its fork of Groot to edit its behavior trees. This package contains the following parts of the system:

• All actions, conditions, and decorators used in the behavior trees
• All behavior trees used on the robot
• An action server to run the behavior trees
• An assistant to streamline maintainance on the system
• Utilties for testing the health of the system

Package Structure

The package is split up into five main parts:

• Custom node definitions or headers, which are located in include/riptide_autonomy and split up by node type (bt_actions, bt_conditions, and bt_decorators). This is the C++ code that defines the behaviors of the package's custom BT nodes.
• Custom node tests, which are located in test/riptide_autonomy and split up by node type. This is the C++ code that tests the custom node definitions. All tests are written using the GTest framework. Header files for test utilities can be found in include/autonomy_test.
• The doTask executable, which spins up an action server that runs behavior tree XML files on the system.
• The BT XML, located in trees, stores the XML which is run by the doTask executable. The XML workspace is located in trees/.groot/workspace.xml and contains all custom node declarations and subtree definitions. This file cannot actually be run because there is no main tree, but it is used by UWRTs Groot editor to ensure that each executable behavior tree in the trees directory shares the same custom nodes and subtrees.
• The BT assistant, located in src/riptide_autonomy/assistant is a useful tool for performing tedious tasks related to the package.

Running BehaviorTrees

Starting the action server

The doTask node contains an action server which allows for easy running of behavior trees stored in the trees directory. Launch it, along with other important nodes, with the command:

ros2 launch riptide_autonomy2 autonomy.launch.py robot:=<robot name>

The action server should appear as <robot name>/autonomy/run_tree and ingests the riptide_msgs2/action/ExecuteTree action type (see riptide_core for more information).

Running using RViz

Behavior trees can also be run from UWRTs MissionPanel RViz plugin (see riptide_rviz in UWRTs riptide_gui repo for more information). So long as the action server is running, the MissionPanel can be used to select behavior trees found in the trees directory and run them with the press of a button.

LED Status Patterns

UWRT's AUV has strips of LEDs in both cages to indicate robot status to swimmers and operators on the surface. riptide_autonomy commands these LEDs to display colors and patterns to indicate what the behavior is commanding the robot to do. States are set using the SetStatus action. The following table matches status names (which go into the "name" port on the SetStatus node) to their LED behaviors and descriptions.

Status	LED behavior	Description
undefined	Solid white	Invalid status received.
waiting	Solid red	Waiting for kill switch
starting	Slow blink blue	Kill inserted, starting run
moving	Solid green	Positioning for next task
searching	Solid yellow	Searching for next task
aligning	Slow blink purple	Aligning with task
performing	Fast blink blue	Performing task
success	Pulsing green	Tree ended with SUCCESS
failure	Pulsing red	Tree ended with FAILURE
panic	Fast blink red	Tree crashed

Editing BehaviorTrees

Use UWRTs fork of Groot to edit behavior trees used by the system.

Using the BT assistant

The BehaviorTree assistant is a tool that streamlines system-related tasks such as creating nodes, checking system health, rebuilding the project, and generating the C++ sources that register the custom nodes with the BT.CPP library. The tool can be invoked through ROS with the command:

ros2 run riptide_autonomy2 btassistant.py [-h] [-s] [-f]

The tool can also be directly invoked by running the Python script located at:

src/riptide_autonomy/assistant/btassistant.py

The optional flags (-h, -s, -f) are detailed as such:

• -h: Display a help menu and exit
• -s: "silent" mode: only display prompts and output from invoked processes (like colcon).
• -f: "force" mode: assume yes on all prompts.

The tasks the BT assistant can perform are detailed in the below sections.

Creating Nodes (btassistant.py create)

By using the create subcommand, the BT assistant can automatically create new custom nodes and register them with the BT.CPP library. The usage of this subcommand is:

ros2 run riptide_autonomy2 btassistant.py create <action type> <node name> [--no-rebuild]

where action type is the type of action to create, and can be any of the following BT types:

• action - BT Action
• condition - BT Condition
• decorator - BT Decorator

and node name is the name of the new node being created.

Upon generating the necessary files, the command will invoke colcon and rebuild the package unless the --no-rebuild flag is specified.

Checking System Health (btassistant.py check)

The check subcommand evaluates the health of different aspects of the system, ranging from ensuring that every custom node is part of the XML workspace, to invoking the custom nodes' test code. The usage of this subcommand is:

ros2 run riptide_autonomy2 btassistant.py check <module>

where module can be any of the following:

• files - Checks the package's file tree to ensure that every custom node has a "definition" in include/riptide_autonomy and a "test" in test/riptide_autonomy. If the assistant finds a custom node with a definition but no test, or a test but no definition, it will notify the user and prompt them to delete the existing file, add the missing one, or ignore the problem. If changes were made to the file tree at the end of execution, the user will be asked if they would like to rebuild the package.

• behaviortree - The same as running ros2 run riptide_autonomy checkBT. Checks that every custom node in the package is defined in the TreeNodesModel of the XML workspace. This also checks that all ports reported in the XML workspace match those defined by the custom nodes. If any discrepancies are found, the assistant will offer to fix the problem by modifying the XML workspace. This tool will NOT modify any source code. It is up to the user to determine whether modifying the workspace is the best fix, or if it is better to modify source code.

• nodes - This subcommand invokes the tests defined in test/riptide_autonomy. It is roughly equivalent to running the command ros2 run riptide_autonomy testBT, however, because tests are not built by default (for quicker compilation), this subcommand will rebuild autonomy with tests enabled if no testBT executable is detected.

• system - This subcommand invokes the above three checks and reports if any of them failed. This is an effective health check for the entire package.

Reconfiguring The Package (btassistant.py reconfigure_autonomy)

The reconfigure_autonomy subcommand cleans the CMake cache and then rebuilds the project. This forces any new custom nodes to be built if they haven't been already (however, if you use the btassistant.py create subcommand without the --no-rebuild option, you should be fine). This subcommand also provides optional flags to enable building with tests or building in debug mode (needed if running code with breakpoints). The usage of the subcommand is:

ros2 run riptide_autonomy btassistant.py reconfigure_autonomy [--with-tests] [--debug]

where the optional flags do the following:

• --with-tests: Builds the project with tests enabled (-DAUTONOMY_BUILD_TESTS=ON). Use this flag if you wish to invoke the testBT executable.
• --debug: Builds the project with debug mode enabled (-DCMAKE_BUILD_TYPE=DEBUG).

This subcommand is roughly equivalent to running colcon build --packages-select riptide_autonomy with the necessary CMake flags set.

Generating The Registration Sources (btassistant.py generate_registrators)

This subcommand is invoked during the CMake configure step to generate the C++ source files that are compiled into the shared libaries. Realistically, there is no reason to manually invoke this subcommand.

Repo Information

OS Distro	Ubuntu 22.04
ROS Distro	ROS2 Humble
BT.CPP	BT-CPP-v3